Various models of caps, at present, are provided with the above means. However, in the majority of cases, they are equally comprised of a cylindrical body whose upper end is completely closed, while the lower portion includes an inviolable device made up by a severable band interconnected with the said body by means of severable bridges or links and, in addition, the said band is provided with internal means in the form of teeth or a suitable groove to provide coupling action between the bottleneck and the cap when the latter is screwed onto the bottleneck because, at this moment, the teeth or groove will extend beyond a collar disposed on the bottleneck, thereby providing a kind of irreversible grasp, which is to say, regardless of the internal design of the seal, the same is designed to withstand the coupling action between the cap and flask, making it easier for the band to extend beyond the collar but, in an opposite direction, causing said links or bridges to split with ease, thus giving proof that the assembly has been tampered with or, in other words, if the cap is unscrewed, there is no way of avoiding the band being fastened to the collar, causing the separation thereof from the body of the flask, which separation, however, will be incomplete because one of the regular features is also the fact that the band will be practically transformed into a strip, held by one end to the body of the flask and thereby preventing any further attempt of removal, which is an important factor when the flask is of the returnable type.
A regular feature in known caps is that all the bridges split at the same time, which calls for a stronger effort to unscrew the cap and also increases the possibility of failure in the sealing system, while, in some cases, the band remains attached to the bottleneck and needs to be removed when the bottle is returned for a refill.
To overcome the aforementioned inconveniences, Utility Model No. 7,101,554 was created and filed on July 7, 1991, under the same title "FLASK CAP", in which important changes were introduced, all designed so that, when the cap is unscrewed, the band may come apart gradually from the body of the cap, causing the bridges to break almost one at a time, so that almost no effort is required to open the flask and, in addition, a different bridge and a nonseverable connecting section are provided, so that one of the ends of the band or strip may remain attached to the body of the cap. These changes have made it possible for an even more fragile seal to be provided, which makes it impossible for the container to be opened without destroying the seal on the bottleneck and also making it impossible for the seal's strip to remain attached to the bottleneck.